As a rational concept, art has existed since the dawn of ages. The Merriam-Webster online dictionary defines it as "something that is created with imagination and skill and that is beautiful or that expresses important ideas or feelings." Therefore, due to its ubiquitous and ambiguous nature, art can be conveyed and presented through different mediums.
Despite this seeming variety of channels of distribution, and its obviously subjective essence; an argument can be made for the spectacle that is live music to be considered perhaps the ultimate form of artistic expression.
For starters, a musical composition involves a deeply personal creative process on all rhytmic, melodic and lyrical fronts. All these elements are reflective of the composer(s)' ideas, with firsthand variables such as mood, emotions, and memories affecting the process. Most importantly, the author(s) have the firm intention of reaching a desired audience of sorts, conveying a powerful message that will connect them to others through musical resonance.
Fortunately for musicians, the universal, malleable and accessible nature of music can help them overcome obstacles such as language barriers, truly making music a language that we all innately know and can use to communicate despite other shortcomings. This also translates into the live aspect of music, where the enjoyment of music displayed through different outlets such as the iconic head banging, jumping, foot-tapping, and different dancing moves depending on the genre, are all incredibly easy to identify and cognitively associate with the live melodies being played.
Another element of live music that makes it so genuine and humanizing when it comes to expression, is its ability to suspend most people's inhibitions for the duration of the show. A certain song can be a mental trigger for many memories and feelings inside of a person's brain, causing a state of euphoria that can be expressed by dancing and singing alongside a crowd of strangers that most will most likely replicate that behavior. This also applies to performers, for example, on-stage antics at rock concerts can be very exaggerated and eccentric, i.e. the smashing of instruments at the end of the performance.
Lastly, appearance is an integral part of each production. Whether it is the use of face paint, make up and even costumes, theatrics and staging further drive the symbolism and expressionism found in the music. Stage decorations also tend to be ostentatious and match the songs that are being performed, to a point where many artists are known more for their staging than their music, which speaks to the versatility and creative fluidity and flexibility a concert can provide.